1. Field of the Invention
The present invention relates to wound dressings and methods for making same, and in particular to a wound dressing which can be applied to a patient without stretching thereof, and a method for the continuous production of a large number of such wound dressings.
2. Description of the Prior Art
Wound dressings consisting of thin flexible material, such as urethane, having adhesive on one side, which are applied to an open wound of a patient after medical treatment of the wound are known in the art. The flexible nature of the urethane permits the dressing to conform to virtually any contour of the patient at the location where the dressing is applied. The flexibility and thinness of the wound dressing, however, present the problem of applying the dressing to the patient without stretching the dressing. Stretching of the dressing prior to or during application thereof to a patient will momentarily expand the stretchable urethane, and even though the dressing may appear smooth when applied to the patient, the urethane will very quickly thereafter contract after the stretching forces are relieved, thereby causing discomfort to the patient and irritation to the area surrounding the wound. On weak or damaged skin, as in the elderly, the stretching forces can cause serious skin damage, such as an abcess. One proposed solution to the stretching problem was to use heavier polyurethane materials. These heavier materials are not desirable as a wound dressing due to decreased flexibility and less gas permeability.
Another proposed solution to this problem is to provide a flexible but non-stretching backing for the urethane wound dressing which remains in contact with the wound dressing by adhesive while the dressing is being applied to the patient, and is separated from the wound dressing only after the dressing has been placed on the patient, thereby eliminating stretching during application of the dressing. Such a wound dressing is described, for example, in European patent EP 0 066 899 A2. The wound dressing disclosed therein is a film sheet of polyurethane having adhesive on one side thereof which is applied to a patient. A non-stretchable film sheet carrier is pressed against the opposite side of the film sheet. The carrier may be bound to the film sheet either by the adhesion resulting from the urethane film sheet casting process, on a non-stretchable film sheet carrier or by a heat-dependent process to the non-stretchable carrier. A combination polyurethane film and MYLAR(copyright) polyester film (E.I. du Pont de Nemours, Wilmington, Del.) are commercially available. To this combination is added a free film of adhesive with the top adhesive backing left on the urethane film MYLAR(copyright) polyester film. Adhesive backing is peeled away prior to application to a patient. After the adhesive side of the film sheet is brought into contact with a patient, the Mylar(copyright) is peeled from the other side of the film sheet leaving polyurethane on the wound.
Another problem encountered when applying the polyurethane film to the wound is maintaining the sterility of the dressing during the application process. Previous products such as the polyurethane film wound dressings Ensure-It(copyright) (Deseret Medical, Inc.) and POLYSKIN(copyright) transparent dressing (Kendall Company, Boston, Mass.) required contact between fingers and the adhesive surface of the polyurethane film during application, thereby potentially contaminating the adhesive surface adjacent to the wound beneath the polyurethane.
Still another problem is the presence of a tab or tabs remaining on the polyurethane film after application to the wound surface. The presence of a tab often results in a gradual loosening of the polyurethane film to skin adhesive bond resulting in a curling-up of the polyurethane film edge adjacent to the tab.
One solution to this tab problem required a perforation adjacent to the tabs, thereby allowing removal of the tabs after application of the polyurethane film to the skin surface. However, the act of tearing of the tab perforations disturbs the adhesive bond, distorts or stretches the polyurethane film and microbially contaminates the adhesive, thereby resulting in a less secure, less sterile and less comfortable wound dressing.
There has been a long felt need for a polyurethane film product that provides ease of application, maintains sterility and does not require distortion of the film sheet by tearing operations. The tab systems of the present invention meet this need.
Alvarez et al., Infections in Surgery, p. 173, Mar. 1, 1984, presented evidence that a completely occlusive dressing such as hydrocolloid, best promoted the healing rate of wounds up to 96 hours. After longer periods of time, 96 hours or longer, a gas permeable polyurethane film resulted in superior healing rates as measured by collagen synthesis. These results suggest that for some applications the ideal wound dressing would function as a completely occlusive dressing for a first period of time, then function as a semi-occlusive dressing for a second period of time.
The layered construction of wound coverings containing gas permeable polymers has long experienced a problem in manufacturing. The casting of a polymer film sheet, such as polyurethane, on a casting sheet resulted in a weak electrostatic bond (corona coating) between the liner and polymer film sheet. This weak bond was weakly effective at holding the film sheet to the liner. If this liner was used as a cover sheet it was not-replaceable once removed. Wound coverings were limited to the types of liners that could be used as casting sheets for the polymer; such use requires resistance to casting heat. The most common liner being MYLAR(copyright) polyester film, a relatively stiff material not possessing the flexible properties desired in a material suitable for the application as a flexible wound cover contouring agent. A need existed for a production method allowing the insertion of adhesive and the substitution of a more flexible cover sheet.
It is an object of the present invention to provide a non-stretchable wound dressing which can be manufactured by overlying a series of continuous strips.
It is a further object of the present invention to provide such a wound dressing wherein the release characteristics between the wound dressing and the non-stretchable cover sheet can be controlled independently of the release characteristics between the wound dressing and the carrier sheet.
Another object of the invention is to provide a tab system that allows support of the non-stretchable wound dressing following removal of the carrier sheet. Still another object of the invention is to provide a tab system that allows manipulation of the wound dressing without contaminating contact between the sterile polyurethane film adhesive and the wound dressing applier""s manipulating fingers. Yet another object of the invention is the presence of a tab system that prevents contact between the adhesive on the polyurethane film and the adhesive on the non-stretchable cover sheet, such contact being a source of defective applications. One object of the invention is the presence of a tab system that permits application of the wound dressing with one hand, such as self-application to the arm or hand. Another object of the invention is the optional presence of skin binding adhesive on the tabs of the non-stretchable cover sheet which permits the use of the cover sheet as a first 100% occluding wound cover, and following removal of this cover sheet, secondarily permits the semi-occluding polyurethane film to continue to cover the wound.
Yet another object of the invention is the coding of the tabs to indicate the sequential order of utilization of the tabs. Still another object of the invention is a wound dressing incorporating a hierarchy of adhesive strengths wherein the adhesive strength (1) of the bond between carrier sheet and polyurethane film is less than the adhesion strength (2) of the bond between the polyurethane film and the non-stretchable cover sheet, and this adhesion strength (2) is less than adhesive strength (3) of the bond formed between the polyurethane film adhesive and a biological surface or skin.
Yet another object of the invention is to provide a wound dressing wherein the film sheet contains an adhesive free area of less than 90% of the film sheet area, more preferably an adhesive free area of less than 50% of the film sheet area, and most preferably an adhesive free area of less than 30% of the film sheet area. Still another object of the invention is to provide a wound dressing wherein the film sheet contains an absorbent material covering less than 90% of the film sheet area, preferably less than 50% of the film sheet area and most preferably less than 30% of the film sheet area. The absorbent material may contain nothing; it may contain a medication such as an antibiotic, an anti-inflammatory compound, a pharmaceutical compound suitable for transdermal application, or a growth promoting hormone; and it may be opaque to block visualization of the wound and contain absorbent material as insulation to retain warmth in the wound region.
The above objects are inventively achieved in a non-stretchable wound dressing consisting of a thin film of material such as polyurethane having adhesive on one side thereof, and covered on the opposite side with a non-stretchable cover sheet, such as Mylar(copyright), having two spaced tabs on opposite sides thereof. The adhesive side of the wound dressing is in contact with a release surface of a carrier, which may otherwise be comprised of heavy paper. Pulling the first gripping tab 1 lifts the combination wound dressing-cover sheet from the release surface of the carrier, and the second tab 2 provides another gripping area to place this combination over a wound without stretching the urethane sheet and without the necessity of the fingers of the person applying the dressing ever coming into contact with any part of the dressing which will be in contact with the patient, thereby avoiding transfer of dirt and infective microbes. After the combination wound dressing-cover sheet has been placed over the wound, the second tab 2 is pulled and, because the adhesive strength between the patient and the wound dressing is selected to have greater adhesive properties than the adhesive between the cover sheet and the wound dressing, the cover sheet is peeled away from the wound dressing, leaving it in place on the patient without stretching or wrinkling thereof. In one variation, a third tab 3 may be attached to a minor cover sheet located below the second tab 2, tab 2 being attached to the major cover sheet and tab 1.
Various different embodiments utilize a variety of agents and structures to promote easy release of the cover sheet from the wound dressing and/or of the wound dressing from the carrier sheet, among them gauze, and ink containing silicone or paraffin.
An object of the invention is a method of manufacturing wound coverings incorporating:
(a) a tab system for application, wherein roll stations continuously supply the materials for layered assembly of the tab system, and
(b) formation of a packaging envelope as a final layered assembly step wherein the packaging roll stations increase the feed rate of top and bottom packing material wider than the wound coverings such that sufficient excess packing material between wound coverings permit the formation of a package seal capable of maintaining a sterile barrier around the enclosed wound covering.
This method for manufacturing a large number of such wound dressings has a plurality of stands or stations each having a pair of rolls forming a nip, and the upper roll of each station receiving at least one component of the wound dressing package in continuous feed from a supply roll. The various components in this strip form are applied over each other in connected layers. A last station cuts the continuous web of layers so as to produce the individual wound dressings, and the now-cut wound dressings are transferred onto a moving paper web which will form one side of a packaging envelope. The opposite side of the envelope is provided from above, sandwiching the wound dressings therebetween. The speed of the rolls at the station following the web cutting station is slightly higher than the speed of the preceding rolls, thereby providing increased spacing between the cut wound dressings. The top and bottom of the envelope webs are heat sealed or pressure sealed, and the spaces between the separated wound dressings are cut to form individual packaged dressings.
Another object of the invention is a manufacturing process wherein beneath the first tab, a narrow bond is formed between the film sheet adhesive and the cover sheet adhesive thereby insuring the successful removal of the cover sheetxe2x80x94film sheet combination from the carrier sheet upon pulling the first tab. A roller apparatus is utilized to exert pressure on the cover sheet just above the film sheet edge beneath the first tab, thereby insuring that sufficient adhesive bleeds out along the edge of the film sheet and forms a strong bond to the cover sheet adhesive.
Still another objective of the invention is a manufacturing process wherein beneath the second tab, a sheet of material is placed along the edge of the film sheet to insure that no bond is formed by the leaking of film sheet adhesive to contact the cover sheet adhesive. This prevention of a bond forming beneath the second tab, between the two adhesive layers, is critical to insure the reliable removal of the cover sheet from an undistorted film sheet after application to the patient surface. One method of preventing the bond between the adhesive layers beneath the second tab is the presence of a minor cover sheet over the film sheet edge. Attached beneath the inner edge of the minor cover sheet is third tab suitable for removing the minor cover sheet by pulling the third tab in a direction opposite the pulling direction of the second tab. The third tabxe2x80x94minor cover sheet system insures the easy removal of the major cover sheet by physically blocking the formation of a bond between the film sheet adhesive and major cover sheet adhesive. The minor cover sheet is held in place by a narrow band of cover sheet adhesive that binds along the top edge of the film sheet, but that does not extend adhesively to the extended minor carrier sheet.
Yet another object of the invention is a manufacturing process wherein the polyurethane film sheet is applied to a carrier such that the edges of the carrier sheet extend beyond the edges of the film sheet a distance suitable for gripping the extended carrier sheet as a tab but not touching film sheet surface.